Method for informing layers of a protocol stack about the protocol in use

ABSTRACT

A method for transferring information over a data connection in accordance with a protocol stack ( 206, 210 ) comprising first and second protocol layers. The method is characterized in that a protocol identifier is created the value of which is determined by means of the first protocol layers of said protocol stack and which is delivered to the second protocol layers of said protocol stack.

TECHNOLOGICAL FIELD

The invention relates in general to communications protocol stacks. Inparticular the invention relates to information about the protocolsused, which information is communicated between protocol layers.

BACKGROUND OF THE INVENTION

Data communication connections and the protocols used in them areusually depicted using the Open Systems Interconnection (OSI) referencemodel which comprises seven protocol layers. The idea of having protocollayers is that the functions of the layers and the interfaces betweenthem are specified in detail, and a protocol in use in a given layer ofthe protocol stack may be changed into another one when desired. Toensure the interchangeability, the protocol layers only operate on thebasis of information contained in the fields of their own particularprotocol frames.

Future communications networks, especially wireless networks, willemploy terminals which will have different characteristics and some ofwhich will be more versatile than current terminals. As there will beterminals of different qualities, the application software must to acertain extent be able to adapt to the characteristics of the terminals.Some applications may only be used on certain terminals and with certainprotocols, but some of the programs will know how to adapt to thecharacteristics of the terminal and the data connection in use. If aterminal supports multiple protocol stacks, the protocols used can benegotiated when establishing the data connection. So, an applicationprogram does not necessarily have knowledge of the protocol stack onwhich it is running.

Resources management for data networks will be more complicated becauseof a wider selection of terminals, increased number of applications,simultaneous use of different protocol stacks and increased use of thewireless network for packet switched data connections, among otherthings. Problems will be caused especially by the fact that for a reasonor another data networks comprise heterogeneous parts. A packet switcheddata network, for example, may comprise a fixed and wireless part, or aprivate subnetwork in addition to the public fixed packet data network.Specifications of connections must be communicated across theinterfaces, between the different parts of the network: for instance, ifone part has less resources than another, it may be necessary to limitthe amount of information transferred between them, or if differentparts of the network use different meters for the quality of theconnection, these quality parameters will have to be replaced by others.If a connection passes through a different part of the network andreturns to a network of the original kind, the connection after thatsecond interface should be as much as possible like the originalconnection. So, resources management at the interfaces and connectionmappings across the interfaces should be coordinated.

FIG. 1 shows a packet switched data connection according to the priorart over a radio link. The protocol stacks used in the equipment areshown at the bottom, and the top of the protocol stack may bedynamically negotiated. The lowest two protocol layers 103 and 104 arealways the same both in the transmitter (TX) 101 and in the receiver(RX) 102. These protocol layers are associated with the physical linkand its control, in this example with radio wave frequencies,transmission power and possible error correction and retransmissionmethods. In the transmitter of FIG. 1, the top of the protocol stack maybe selected from among three alternatives (105, 106, 107), so thetransmitter may connect with receivers that support any of thesealternatives. In the receiver of FIG. 1, the top of the protocol stackmay be selected from among two alternatives (105, 106). The protocolsused are negotiated during the connection setup stage so that bothapparatus in FIG. 1 will use the same top of the protocol stack, either105 or 106.

FIG. 2 shows a prior-art packet switched data connection at theinterface between a fixed network and a wireless mobile radio accessnetwork. The radio access network comprises base stations and radionetwork controllers. A wireless terminal 201 is connected via a basestation 202 to a radio network controller 203. The radio networkcontroller is connected to a network node 204 at the border of the radioaccess network and the fixed network. By way of example, a secondterminal 205 is shown connected directly to the network node. Morelikely it will be connected to the network node via routers and othernetwork elements.

FIG. 2 shows, at the bottom, the protocol stacks 206–210 of theapparatus. Each protocol layer's protocol is denoted by the letter Lplus the number of the protocol layer. In the lowest two protocollayers, which are different for the fixed network and wireless network,the protocols are marked by symbols in which the letter C refers to afixed network and the letter R stands for radio access network.

The radio access network employs two different first-layer protocols,which are in FIG. 2 denoted by symbols L1/R1 and L1/R2. Protocol L1/R1is associated with the radio interface between a wireless terminal andbase station, so it is used in the protocol stack 206 of the wirelessterminal and in the protocol stack 207 of the base station at the radiointerface side. Protocol L1/R2 is associated with radio access networkconnections over a fixed line, so it is used in the base stationprotocol stack at the radio network controller side, in the radionetwork controller's protocol stack, and in the protocol stack 209 ofthe network node 204 at the radio access network side. All radio accessnetwork elements as well as the wireless terminal use the same protocolL2/R in the second protocol layer or, if there are sublayers in thesecond protocol layer, at least its highest sublayer uses the sameprotocol. In the radio access network elements, protocol stacks 207 and208 often cover only the lowest two layers.

At the fixed network side, between apparatus 204 and 205, the packetswitched data connection is carried on top of a so-called core networkbearer service. The term bearer service refers in this context mainly tothe second layer of the protocol stack. The characteristics, say, datatransfer capacity or quality, of this core network bearer service areinfluenced by the physical connections used and the methods associatedtherewith. The quality of the packet switched data connection proper isusually specified at a higher level, e.g. as quality of service in theIPv6 protocol in the third protocol layer, and the bearer service ischosen such that it can meet the connection quality requirements.

In the network node 203 or alternatively in node 204 the packet switcheddata connection carried upon a core network bearer service has to betaken on top of a radio access bearer service. In a wireless mobileradio access network there are a certain number of different radioaccess bearer services, and the qualities that describe them includee.g. the transfer rate, bit error rate (BER) and whether or not thereception of a transferred packet is verified as well as the size of thetransfer window used for the verification. The network node must map thecore network bearer service to a radio access bearer service that hasenough capacity to guarantee a desired connection quality but withoutwasting radio resources, however. The network node's protocol stack 209uses in the lowest two layers of the protocol stack fixed networkprotocols at the fixed network side, and radio access network protocolsat the radio access network side.

The third-layer protocol is determined on the basis of the protocol usedin the packet switched data network. When a packet switched dataconnection is established, terminals 201 and 205 may negotiate theprotocols used for the end-to-end connection. These protocols usuallyare protocols on top of the third protocol layer, and they are identical(or at least compatible) in the protocol stack 206 of the wirelessterminal and protocol stack 210 of the second terminal. The upperprotocol layers do not know that the end-to-end connection between theterminals has crossed a radio interface at some point; as far as theyare concerned, the connection could as well be an end-to-end fixedconnection.

Prior-art end-to-end connections capable of utilizing dynamicallynegotiated protocol stacks involve certain problems. For example, insituations where an application knows how to present data as eithertext, pictures or video, it could exclude the video if it knew that thecapacity of the data connection is insufficient to transfer a videoimage. Moreover, the lower protocol layers do not have knowledge of thecapabilities of the upper protocol layers as regards reception of datapackets that are in disarray and some of which are missing. If a lowerprotocol layer does not make sure that the data packets are in order anda higher protocol expects them to be, problems are likely to occur.

A prior-art multimedia application may use either one or more dataconnections for the transfer of data. For example, data in text formatmay be transferred via one connection, a video image via a second andsound via a third one, and, in addition, the application may all thetime have a connection open through which to transfer commandsassociated with the synchronization of the objects presented. Anotheralternative is that these data travel through a single data connection,i.e. the application multiplexes the data streams into a single datastream and an application at the other end of the connectiondemultiplexes them so that they become separate again. If an applicationuses multiple separate data connections, problems arise if the lowerprotocol layers do not understand that these connections belong to oneand the same application. In a situation where only part of the data canbe delivered because of scarce resources, this may result in that themost important packet switched data connection, in which the controlcommands are transferred, is slowed down or even disconnected.

For prior-art packet switched data network interfaces it is oftennecessary to either prioritize the data to be transferred, because ofscarcity of data transfer resources, or map the connection qualitydefined in a certain manner to a connection defined by means of otherparameters. In these situations, decision-making in the lower protocollayers would benefit if those layers had knowledge of the informationtransferred over the connection. For example, knowledge of the typicaldata transfer rate for the connection would help decide how muchresources should be reserved for the connection. In the case ofprioritization, more detailed knowledge about the informationtransferred (whether it is, say, control commands associated with theapplication software or presentable data) would help in deciding what isthe most important information.

SUMMARY OF THE INVENTION

An object of the invention is to provide a method with which it ispossible to characterize data for lower protocol layers and thecharacteristics of the data connection for upper protocol layers. It isadvantageous that the method is a hierarchical one, i.e. it is firstgiven a rough description which can then be particularized. It is alsoadvantageous that the description is short.

The objects of the invention are achieved by a method with which it ispossible to indicate the protocols or parts of protocols used in givenprotocol layers to other layers of a protocol stack.

The method according to the invention for transferring information overa data connection in accordance with a protocol stack comprising firstand second protocol layers

is characterized in that

-   -   a protocol identifier is created,    -   a value for said protocol identifier is determined by means of        the first protocol layers in said protocol stack, and    -   said protocol identifier is delivered to the second protocol        layers in said protocol stack.

The upper-layer protocols or their coding methods, for example,characterize the amount of data transferred over a connection as well asburstiness of data, for example. Thus they describe the requirements onthe data transfer and, thereby, on the lower protocol layers. Theprotocols also tell, at least partly, what kind of data flow through thepacket switched data connection. A method according to the invention,which identifies the protocols of an upper layer or layers, thus tellsthe lower protocol layers what kind of data they are transferring. Thusit becomes possible to handle the data packets according to theircontents. For example, if the upper-layer protocols are such that theyoperate better when the data packets are delivered reliably and in thecorrect order, the lower-layer protocols may make sure that thishappens.

Correspondingly, certain lower-layer protocols are associated with dataconnections that have a limited transfer capacity. Thus, using themethod according to the invention the upper-layer protocols may obtaininformation about the data connection. For example, the transfer ratefor a high-speed data connection in a GSM (Global System for MobileCommunications) network is a multiple of 9.6 or 14.4 kbps and normallynot more than 28.8 kbps. In a third-generation UMTS (Universal MobileTelecommunications System) network the maximum data transfer capacity is2 Mbps. If a terminal that can operate in both UMTS and GSM uses themethod according to the invention to indicate to an application at theother end of the connection the protocol used in the link layer, theapplication may use video to present the data, depending on the datatransfer rate.

If the method according to the invention is used to communicateinformation from the upper protocols to the lower protocol layers, theinformation about the protocol may be added to the protocol frame.Advantageously a field is reserved in the frame for this purpose.Information in the protocol frame reaches all lower protocol layers inthe same terminal, network element, network interface and/or terminal atthe other end of the connection. If information is to be sent from thelower protocols to the higher ones, it has to be done indirectly. In aterminal, for example, the information about the lower protocols can belocally signaled to a higher protocol which places that information inits protocol frame or inserts it in the data to be transferred. So theinformation travels over the connection and reaches the upper protocollayers in the network element, network interface and/or terminal at theother end of the connection.

In the method according to the invention the information aboutprotocols, protocol versions or protocol elements may be transferred inprotocol frames of a certain protocol layer, in a field reserved forthat purpose. The advantage of using a special field is that the lowerprotocols need not go through and analyze the whole contents of thepackets, but an identifier found at a certain location of a packetidentifies the protocols. Another alternative is to communicate thisinformation when setting up the connection. In that case it may betransferred either in a data packet (say, protocol field) associatedwith the handshake procedure or in a control connection separate fromthe packet switched data connection used for the data transfer if such aconnection is provided.

Since the protocols used in data communications networks are widelyknown and ratified by standardizing bodies or correspondingorganizations, information about them may be communicated using shortidentifiers. In addition, the identifier according to the invention forcommunicating protocol information is advantageously a hierarchical datastructure, i.e. a protocol or protocols is/are first identified roughly,whereafter a more detailed definition is given. Such a hierarchical datastructure is flexible and fast to process as it quickly indicateswhether the more detailed part contains relevant information.

Information communicated by the method according to the invention may beutilized locally in the same terminal, in a network element at thenetwork interface or in a terminal at the other end of the connection.The invention takes no position on how to decide in which layers theprotocols are the most important as regards data transfer or datapresentation formats, for instance, or where and how this information isutilized in the other protocol layers.

BRIEF DESCRIPTION OF DRAWINGS

The invention is below described in greater detail referring to thepreferred embodiments of the invention and to the appended drawing, inwhich

FIG. 1 shows a prior-art packet switched data connection over a radiolink with the protocol stacks,

FIG. 2 shows a prior-art packet switched data connection over the airinterface of a wireless mobile network with the protocol stacks,

FIG. 3 shows a data communication method according to two preferredembodiments of the invention,

FIG. 4 shows in greater detail a protocol layer associated with a thirdpreferred embodiment of the invention,

FIG. 5 shows a data structure used for communicating protocolinformation according to a fourth preferred embodiment of the invention,and

FIG. 6 shows a schematic of an apparatus that employs the methodaccording to a preferred embodiment of the invention.

Reference was already made to FIGS. 1 and 2 in the description of theprior art.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 3 schematically illustrates two methods according to a preferredembodiment of the invention for communicating information about theprotocols in use. The figure shows protocol frames associated with acertain packet switched data connection: the packet at the far right hasbeen sent first. In each protocol frame, oblique lines indicate thatportion of the protocol frame which communicates information about theprotocols in use.

The upper part of FIG. 3 shows a method in which the protocol frames301–306 used for the data transfer proper carry protocol information aswell. By way of example, each protocol frame in the figure contains aprotocol identifier 307 (say, a protocol field). Depending on thesituation, the identifier may be in every protocol frame or only in partof the frames, e.g. in every hundredth frame.

The bottom part of FIG. 3 shows a method in which the information aboutthe protocols used is communicated at the beginning of the connection.The packets 308–313 associated with the data transfer are inchronological order from right to left. In this case the informationabout the protocols used is in identifier 314 which is in the firstprotocol frame 308 of the packet switched data connection, but it ismore common that the information is transferred in one or morehandshaking messages at the beginning of the connection. Anotheralternative is that the information is communicated via a separatecontrol connection at the beginning of the connection. For example, inmobile networks a terminal usually has a control connection over the airinterface and radio access network to a network node on the border ofthe radio access network, i.e. the control connection exists between theterminal 201 and network element 204 in FIG. 2. This connection may beone of the so-called call control, session management, mobilitymanagement or radio resource management (L3) connections and it relatese.g. to the mobility management of the terminal, to the sessionmanagement and/or to the management of the frequencies and transmissionpower used in the radio transmission. It may also be established betweenthe terminal and a switch (not shown in FIG. 2) or another apparatusperforming control functions. The information about the protocols usedin the packet switched data connection may also be transferred via thiscontrol connection when opening the packet switched data connection.

FIG. 4 shows a situation which utilizes a preferred embodiment of theinvention. FIG. 4 depicts in more detail the structure of the secondprotocol layer of a radio access network in the packet switched dataconnection of FIG. 2 in an UMTS network. In an UMTS network, the packetswitched data connections associated with a certain terminal orapplication may be linked together by means of an identifier called apacket switched data protocol context.

At the radio access network side the second protocol layer comprises twosublayers: a link access control (LAC) protocol and media access control(MAC) protocol. FIG. 4 illustrates the operation of the LAC protocol:the third protocol layer is above interface 401 and the MAC layer isbelow interface 423. The layer 3 compatibility entity (L3CE; essentiallyequal to PDCP or Packet Data Convergence Protocol) 407 adjacent to thethird protocol layer comprises an administrative unit 408 and thecompatibility unit 409 proper. The L3CE is responsible for recognizingthe data transfer needs of the packet switched data protocol contextsand for presenting said needs to radio bearer services. Network serviceaccess points 403–406 are specified for the upper interface of the L3CEsuch that each access point has a network service access pointidentifier (NSAPI) of its own. FIG. 4 shows four network service accesspoints by way of example. The L3CE administrative unit 408 has a networkservice access point 402 of its own.

Each packet switched data protocol context has at its disposal at leastone network service access point via which data are transferred to thecompatibility unit. At the lower interface 410 of the L3CE there areservice access points 412–415 via which data are transferred to radioaccess bearer services. Each service access point with itscharacteristics corresponds to a certain type of radio access bearerservice and there are as many of them as there are possible differentradio access bearer services (FIG. 4 shows four service access pointscorresponding to four different radio access bearer services). Serviceaccess point 411 is associated with data communications between theadministrative units of the various layers.

Operation of the compatibility unit 409 is controlled through theadministrative unit 408 and it has knowledge of the packet switched dataprotocol contexts' data transfer quality and quantity requirementsagreed during the connection setup stage. However its main function isto flexibly map the network service access points to the service accesspoints according to the data transfer needs of each particular networkservice access point and to limit the data transfer if an attempt ismade to use a transfer rate that exceeds the resources reserved for thepacket switched data protocol context in question. It distributes thedata packets coming through the network service access points to severalservice access points if they have different connection qualityrequirements. It is possible to direct data packets from multiplenetwork service access points to one and the same service access point,i.e. a single radio access bearer service may carry information arrivingthrough several network service access points. The compatibility unitmay also perform data or protocol field packing.

Logical link entities 419–422 in the logical link control (LLC) layer416 control the data transfer over individual radio access bearerservices. There is one logical link entity per each service accesspoint. These entities use their own protocol structures into the datafields of which they place the data coming from the compatibility unit409 via the service access point. A logical link management (LLM) entity417 which controls the logical link entities is responsible, among otherthings, for the establishment and termination of the logical linkconnections, setting of initial parameters of a logical link, handlingof certain error conditions and for the communication of logical linkcontrol parameters between terminals. It communicates with the LLMentities of other network elements in the radio access network through alogical control link unit 418. From the LLC layer the LLC protocolframes are transferred across the LAC-MAC interface 423 at point 424.

In a preferred embodiment of the invention a network node 204 at theinterface of the fixed network and radio access network analyzes whatprotocols are used in the packet switched data connections. Each logicallink entity of this network node adds to its protocol frame (all or justpart of them or only during the handshake) a protocol identifier whichindicates the higher protocols used. Information about these protocolsarrives at the logical link entities via the LLM entity 417. A protocolidentifier may be utilized both for selecting a radio access bearerservice for a packet switched data connection and for managing radioaccess bearer services. The protocol identifier may be especiallyhelpful when solving in the MAC layer problems such as repeatedretransmissions caused by traffic congestion or transmission deadlocks.For example, selection of retransmission mode, size of possibleacknowledge window and adjustment of that size, management of LLCpackets, and estimation of the quantity of data transferred arefunctions where the identification of higher protocols is useful. If,for example, it is known that an application requires real-time datatransfer, the radio access bearer service will not carry outretransmissions and tries to send the packets in correct order.

FIG. 5 shows a hierarchical data structure 500 according to a preferredembodiment of the invention which identifies protocols in amultiprotocol environment. It is used e.g. in a radio access network tocommunicate information between the LLC and MAC layers shown in FIG. 4.The protocol identifier may be placed either in a special field in theprotocol frame or within the data proper. The protocol identifier shownin FIG. 5 is two bytes long: the bytes are represented as horizontalrows and bits as vertical columns, the least significant bit beingfarthest to the right.

The most significant bit 501 in the first byte is a so-called poll/final(PF) bit the meaning of which depends on the type of protocol frame inthe protocol field of which the protocol identifier is placed. The nextfour bits 502 are used for rough protocol identification, so the fieldcould be called a protocol content identifier, for example. Each ofthese four bits is a so-called flag, indicating whether a given protocolis in use. The bottom part of FIG. 5 shows the structure of the protocolcontent identifier 502 in more detail. The protocols chosen are datacommunication protocols typically used in packet switched networks. Forexample, the first IP (Internet Protocol) identifier in the protocolcontent identifier is associated with the network-layer protocol: 0indicates that the network protocol used is not IP, and 1 indicates thatthe protocol is IP. The second PR (Packet Radio) identifier isassociated with the wireless packet switched network used: 0 indicatesthat a GPRS (General Packet Radio Service) network is not used, and 1indicates that a GPRS network is used. The third TU (TransmissionControl Protocol/User Datagram Protocol) identifier distinguishesbetween the TCP and UDP protocols: 0 corresponds to the use of UDP and 1corresponds to the use of TCP. The fourth AP (Application Protocol)identifier indicates whether or not the data structure describes theapplication protocol in more detail (0 means no, 1 means yes).

The last three bits in the first byte of the protocol identifier 500constitute a protocol field 503 which defines the application protocolin use. The field could be called a protocol content identity group, forexample. If the IP identifier is 1 in the protocol content identifier,value 000 in the protocol content identity group corresponds to the IPv4protocol and value 001 to the IPv6 protocol, for example. If the APidentifier is 1 in the protocol content identifier, value 000 in theprotocol content identity group corresponds to Hypertext TransferProtocol (HTTP), 001 corresponds to the lighter Wireless ApplicationProtocol (WAP) used for wireless connections, 010 corresponds to theMHEG application protocol designed for the presentation of multimediaand hypermedia, and 011 corresponds to JAVA protocol. If it is desiredto communicate information about both the IP version and applicationprotocols, this can be accomplished e.g. such that in every other frame,in which the protocol identifier is placed, the IP identifier value is 1and AP identifier value 0 (so the protocol content identity groupindicates the IP version) and in every other frame the IP identifiervalue is 0 and the AP value is 1 (the protocol content identity groupindicates the application protocol). Other ways of communicatinginformation about the both items include e.g. specifying the protocolidentifier such that it has longer fields or that there are more ofthem. Then it is possible to communicate more information in oneprotocol identifier.

The second byte 504 in the data structure 500 is a content descriptor inwhich each bit serves as a flag. Thus, eight protocols may beidentified, and the least significant bit in the byte, for example,corresponds to the highest-layer protocol. A content descriptor isspecified for the protocol groups that can be identified in the protocolcontent identity group. For example, the following flags have beenspecified for the WAP group, starting from the least significant bit:Wireless Application Environment (WAE), Wireless Session Protocol (WSP),Wireless Transaction Protocol (WTP), Wireless Transport Layer Security(WTLS), and Wireless Datagram Protocol (WDP). Similarly, specified forthe MHEG group are the MHEG control, MHEG startup container, MHEGobject, and MHEG link. Packets marked with these descriptors containcertain type of information associated with the MHEG application, e.g.MHEG control packets contain control and synchronization information forthe application presenting the multimedia objects.

A preferred embodiment of the invention is to use a protocol identifierin a situation in which application software, say a multimediaapplication, uses several separate data connections. If the multimediaobjects are presented using the MHEG format, for example, theabove-described or a corresponding protocol identifier may be used toidentify said connections as belonging to one and the same application.These data connections may thus be controlled in a consistent manner atthe radio access network interface, for example. Thus e.g. a situationis avoided in which the multimedia objects are successfully delivered tothe other end of the connection but the control commands necessary fortheir presentation are not delivered because of lacking resources.

FIG. 6 shows an apparatus which applies the method according to apreferred embodiment of the invention. The apparatus 600 is acommunications device, shown here as a wireless terminal. Operation ofthe apparatus is controlled by a control unit 601 which is responsible,among other things, for the protocol stack 602 associated with datacommunications. The method according to a preferred embodiment of theinvention is applied to the second protocol layer in FIG. 6. By way ofexample, its structure is the same as in FIG. 4, and also shown in FIG.6 are the compatibility layer 407 adjacent to the third layer and thelogical link control layer 416. Elements and interfaces of these layersare not named in FIG. 6 but they are the same as in FIG. 4. Theapparatus shown in FIG. 6 may include in LLC protocol frames informationabout the protocols of other layers e.g. so as to be used by alower-layer protocol, and it can read information placed in these framesby another apparatus.

The protocol identifier structure and field contents described above byway of example do not limit the invention to the two-byte identifierdescribed above which comprises the abovementioned fields. Thehierarchical protocol identifier according to the invention may alsohave a different structure, and the protocols that can be identified bymeans of the identifier may be others than those named above.

The protocol identifier according to the invention need not behierarchical. The protocol identifier may comprise one or more fieldseach of which identifies a protocol or protocol element, but theprotocol identifier does not contain a structure that could be used todeduce the relationship between the objects identified by the fields.Consecutive fields in the protocol identifier may e.g. identify thecodec used for the coding of a video image and a packet radio networkalong the data connection. Such a protocol identifier is also inaccordance with the invention.

A protocol may also denote the contents of information transferred. Theprotocol identifier may indicate e.g. whether the informationtransferred is speech, video image or data in general. In the cases ofspeech and video it is also possible to identify e.g. the codec used forspeech or video image coding, the version number of the codec or thestandard with which the bit stream produced by the codec complies.

Although it was above described the use of the method according to theinvention mainly at the interface between a fixed network and radioaccess network, the application of the invention is not limited to thatparticular interface.

Above it was described how the method according to the invention may beused primarily in the management of a data connection, selection of aninformation presentation format, and in the prioritization ofinformation to be transferred. These examples however do not limit theuse of the invention solely to these purposes.

1. A method for transferring information over a data connectionaccording to a protocol stack where certain first protocol layers andcertain second protocol layers exist, comprising: creating a protocolidentifier; determining a value for said protocol identifier inaccordance with the first protocol layers in said protocol stack;signaling said protocol identifier to the second protocol layers in saidprotocol stack; adapting said protocol identifier so as to compriseelements including a first element and a second element; determiningeach element of said protocol identifier on the basis of a certain partof the first protocol layers; and determining said second element sothat it defines in more detail a certain part of the first protocollayers generally defined by said first element.